Stability calculation and test methods for long-span railway bridge Q500 high-strength steel compression rod

Abstract

The invention discloses a stability test method for a long-span railway bridge Q500 high-strength steel compression rod. The method includes the steps of: (1) determining a compression rod stable load apparatus for a long-span railway bridge; (2) selecting a Q500 high-strength steel test sample, which has an I-shaped or a case-shaped cross section, as a compression rod; (3) arranging a strain piece and a displacement meter on the compression rod; (4) performing step-by-step loading onto the compression rod through a test loading machine; (5) measuring out-plane displacement of the middle of the compression rod through the displacement meter and measuring the stress on the compression rod through the strain piece; and (6) determining whether the compression rod is instable according to the out-plane displacement of the middle of the compression rod and maximum stress on the cross section of the middle of the compression rod, and analyzing the relationship of the out-plane displacement and different loads. The invention also provides a stability calculation method for the long-span railway bridge Q500 high-strength steel compression rod. The methods theoretically analyzes the relationship between initial defect, material property, residual stress and the like and stability of the compression rod, and experimentally analyzes influence on complete stability of the compression rod due to the residual stress.

Description

technical field [0001] The invention relates to the technical field of railway bridges, in particular to a method for calculating and testing the stability of Q500 high-strength steel pressure bars of large-span railway bridges. Background technique [0002] Some indicators in the construction of long-span steel bridges in my country have surpassed the world's advanced level, but basic theoretical research lags far behind, seriously lagging behind engineering practice. With the development of bridge construction in China, the span of steel bridges continues to increase, high-strength steel is widely used and developed into a fully welded form, towering towers and thin-walled box girders reduce the overall and local stiffness of the structure, and stability problems appear. More important than ever, there is an urgent need for in-depth theoretical research and model tests on the stability ultimate bearing capacity of steel bridge structures. The study of the stability ultima...

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Problems solved by technology

[0005] 1. The support devices of the large-scale pressure bar stability test are not unified, mainly including double knife edge supports and spherical hinge supports. Different support forms have certain influence on the test results;

[0006] 2. The ultimate bearing capacity of the compression bar stability test of a large-scale full-scale bridge is very large, and a large-tonnage loading machine needs to be configured. The loading capacity of the general laboratory loading equipment is difficult to meet the test requirements. Therefore, the current compression bar stability test often uses a scale model. The residual stress distribution of the reduced-scale model may be different from that of the full-scale model;

[0007] 3. Residual stress is an important parameter affecting the stability of the compression bar. Although the residual stress test was carried out in the previous research on railway steel bridges, it did not directly reflect the influence of the residual stress on the stability of the compression bar through the test;

[0008] 4. In previous studies on the stability of compression bars of railway steel bridges, the highest-strength steel was only 420MPa, while higher-grade Q500q steel has been used in the Hutong Yangtze River Bridge and Zhenjiang Yangtze River Bridge. Due to the influence of building height restrictions, high-strength steel Q500q Although the length of the bar does not increase significantly, the cross-section decreases accordingly. Therefore, compared with low-strength steel, the slenderness ratio increases significantly, and the stability problem becomes more prominent. However, there is no relevant research on the stability of Q500q compression bar so far. ;

[0009] 5. The initial defects (initial loading eccentricity and initial bending of the bar) are another important factor affecting the stability of the compression bar. However, the magnitude of the initial defects in the actual bar is random. Previous studies have made statistical induction on the initial defects. The calculation formula of the initial defect is obtained, but there is no relevant research on the degree of influence of the initial defect on the stability of the compression bar

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